1. Field of the Invention
The present invention relates to a sintered alloy for valve seats in internal combustion engines.
2. Description of the Related Art
Valve seats in internal combustion engines must have good heat-resistance and wear-resistance properties due to constant exposure to high temperature gases and repeated high-pressure contact with the valve. To achieve these properties, ferrous sintered alloys in which high alloy powder particles with high hardness are dispersed into the matrix to improve wear-resistance have been utilized. Further, in diesel engines running under severe heat conditions, and in gas engines not prone to produce products by combustion and oxidized film at the contact surface with the valve and easily prone to metal contact; a sintered alloy for valve seats with excellent wear-resistance was disclosed (Japanese Patent No. 3186816) using alloy tool steel powder at the matrix to raise the heat-resistance of the matrix; using multiple high alloy powder particles of differing hardness and calcium fluoride as a solid lubricant dispersed into the matrix, and in addition infiltrating copper or copper alloys into the pores of the base material to improve the strength and thermal conductivity of the sintered compact.
However, even better wear-resistance is required as diesel and gas engine output increases and service life grows longer.